Expression of VLA-4 on peripheral mononuclear cells in patients on chronic haemodialysis with carpal tunnel syndrome.

BACKGROUND

Carpal tunnel syndrome (CTS) is a major complication in long-term haemodialysis patients and is thought to be a form of haemodialysis-associated amyloidosis. CTS may be due to the deposition of amyloid as well as local inflammatory process in the carpal tunnel. Although macrophage-like cells infiltrating the tenosynovium of carpal tunnel are known to express mRNA for adhesion molecules, the level of expression of adhesion molecules on peripheral blood mononuclear cells (PBMC) in patients with CTS is unknown.

METHODS

We compared the expression of very late activation antigen (VLA-4) on PBMC by flow cytometry in 14 patients on haemodialysis (6-21 years) with CTS, nine on haemodialysis (1-6 years) but without CTS and six patients on chronic ambulatory peritoneal dialysis (CAPD, 1-5 years) without CTS.

RESULTS

The expression of VLA-4 on peripheral lymphocytes was not different among the groups. However, the FACScan fluorescence histogram of VLA-4 expression on peripheral monocytes showed a bimodal pattern in the CTS group, and the rate of the high intensity portion of the expressed VLA-4 on monocytes was significantly higher in CTS than other groups (P<0.05). The observed differences were not based on differences in the type of the dialysis membrane. We also examined the adhesion of PBMC to fibronectin-coated plates. The number of adherent PBMC was significantly higher in patients with CTS than in other groups (P<0.05).

CONCLUSION

Our results suggest that increased expression of VLA-4 on peripheral monocytes and augmented adhesion capacity of PBMC to fibronectin may be involved in the development of CTS in haemodialysis patients.